Lydon J M, Rykers K L
East Melbourne Radiation Oncology Centre, VIC, Australia.
Phys Med Biol. 1996 Jul;41(7):1217-25. doi: 10.1088/0031-9155/41/7/010.
One feature of the dynamic wedge is the improved flatness of the beam profile in the nonwedged direction when compared to fixed wedges. Profiles in the nonwedged direction for fixed wedges show a fall-off in dose away from the central axis when compared to the open field profile. This study will show that there is no significant difference between open field profiles and nonwedged direction profiles for dynamically wedged beams. The implications are that the dynamic wedge offers an improved dose distribution in the nonwedged direction that can be modelled by approximating the dynamically wedged field to an open field. This is possible as both the profiles and depth doses of the dynamically wedged fields match those of the open fields, if normalized to dmax of the same field size. For treatment planning purposes the effective wedge factor (EWF) provides a normalization factor for the open field depth dose data set. Data will be presented to demonstrate that the EWF shows relatively little variation with depth and can be treated as being independent of field size in the nonwedged direction.
动态楔形板的一个特点是，与固定楔形板相比，其射野轮廓在非楔形方向上的平坦度有所提高。与开放野轮廓相比，固定楔形板在非楔形方向上的轮廓显示，远离中心轴处剂量下降。本研究将表明，动态楔形射野的开放野轮廓与非楔形方向轮廓之间无显著差异。这意味着动态楔形板在非楔形方向上提供了更好的剂量分布，通过将动态楔形野近似为开放野即可进行建模。如果将动态楔形野的轮廓和深度剂量归一化为相同野大小的最大剂量深度（dmax），那么这是可行的，因为动态楔形野的轮廓和深度剂量与开放野的相匹配。为了治疗计划的目的，有效楔形因子（EWF）为开放野深度剂量数据集提供了一个归一化因子。将给出数据以证明，EWF随深度的变化相对较小，在非楔形方向上可视为与野大小无关。
